There are many characters in popular culture that, even if it not's admitted by their creators, we all know and accept that they're part of the LGBTQ+ community.
For example, Zangief from 'Street Fighter II' is 100% gay. Likewise, Spongebob Squarepants is and always has been a member of the LGBTQ+ community. It's only just now that Nickelodeon have officially confirmed it during Pride Month.
The network tweeted a photo of Spongebob Squarepants, Korra from 'The Legends of Korra', and Schwoz Schwartz from 'Henry Danger' above a message about celebrating Pride with members of the LGBTQ+ community.
— Nickel🎃deon (@Nickelodeon) June 13, 2020
For the record, nobody's really sure whether or not Spongebob is gay or bisexual, with the creator Stephen Hillenberg claiming in 2007 that he considered Spongebob to be "almost asexual." That hasn't stopped conservative Christian groups in the US arguing that Spongebob was promoting homosexuality with some of its episodes.
In fact, as recent as 2014, the Education Minister of Kazakhstan, Zabira Orazalieva, described Spongebob as "a self-absorbed hooligan", so who knows what to think?
Either way, if Spongebob is living his truth and he's happy, then it's not for any of us to judge him.